rebel forces are now taking the fight directly to the assad regime inside the capital damascus with a deadly explosion near the arab red crescent building and pitch battles for key airfields outside the city. >> it is clear regime forces are being grounded down and they are losing. >> president bashar assad already killed estimated 40,000 people. president obama top aids will fear the fighting take on gruesome character. >> we remained very concerned. very concerned. as the opposition advances on damascus. that the regime might very well consider the use of chemical weapons. >> indeed, the senior officials confirm that syrian technicians mixed unknown quantity of the nerve agent seron and loaded on what officials believe are breakable canisters, aerosol form to be dropped from above. in dublin, secretary of state clinton met twice with the russian foreign minister. the russian dumah leader close to vladimir putin told interfax, "we have shared and do share the opinion the existing government in syria should carry out the function time has shown that the task is beyond its strength. >>